Biphasic liquids defined by the general fact that the liquid is divided into two phases are not new. In some of these liquids, one layer is an aqueous layer and the second layer is a water inmmiscible oily material, while in others both layers are aqueous based.
U.S. Pat. No. 3,718,609 issued to Weimer on Feb. 27, 1973 discloses a liquid detergent composition having an aqueous layer and a layer of liquid water immiscible oily material. When shaken, the liquid forms a temporary oil-in-water emulsion.
Similarly, U.S. Pat. No. 3,810,478, issued to Olson Jr. et al. on May 14, 1974, discloses a two-phase shampoo composition made by preparing substantially polar and lipophilic portions of a shampoo composition.
Biphasic compositions comprising an upper and lower aqueous phase are also disclosed in the art. U.S. Pat. No. 6,429,177 issued to Williams et al. on Aug. 6, 2002 discloses biphasic compositions including 5 to 35% surfactant; 1 to 12% thickener; 4 to 20% polyalkylene glycol; and a sufficient amount of non-chelating mineral salt to induce phase separation.
U.S. Pat. No. 6,180,587 issued to Fuller et al. on Jan. 30, 2001 disclose multiphase cleansing compositions having at least 1% of a polymer or copolymer selected from the group consisting of polyacrylate, polystyrene sulfonate, polyvinylpyrrolidone, maleic anhydride and their mixtures.
EP 0,116,422 to Harmer published on Apr. 6, 1988 also discloses multi-layered compositions in which two liquids are dispersible and which separate on standing. Sodium hexamataphosphate is a preferred biphasic inducing agent required in these compositions.
In U.S. Pat. No. 6,787,511 issued to Patel et al. on Sep. 7, 2004, and U.S. Pat. No. 6,727,209 issued to Pereira et al. on Apr. 27, 2004, the current inventors reported that polydextrose of molecular weight between about 600 and about 3,000 Daltons, used alone or in combination with a salt such as MgSO4 and/or sucrose, induced biphasic liquid formation. While these compositions are adequate, they do not have a particularly high viscosity, particularly the type of viscosity suitable for liquid cleansers targeted to personal cleansing (e.g., shower gels and shampoos). One of the goals of the subject invention was to provide small amounts (e.g., under 1% by wt.) of high molecular weight polymers which could raise the viscosity to levels more suitable for such shower gels and/or shampoos.
In a co-pending application filed on Dec. 28, 2004 to Patel et al., applicants disclose specific biphasic inducing agents (BIA) that can be used alone or in combination with polydextrose and/or salt. Two classes of the new BIA are specific polysaccharides that surprisingly have much higher molecular weights than the optimal polydextrose oligomers described in U.S. Pat. Nos. 6,787,511 and 6,727,209 noted above; and intermediate ethoxylates of fatty esters or fatty acids. These BIAs can be used alone and are used for purpose of economy or to provide opacity. The high MW polymers of the subject invention, by contrast, are always used as adjunct materials (i.e., less than 1% by wt.) and are specifically used to enhance viscosity of previously known biphasic compositions (for example as taught in U.S. Pat. No. 6,787,511 or U.S. Pat. No. 6,727,209). Moreover, they enhance viscosity while retaining ability to induce phase separation in the compositions.
As noted, the present invention relates to use of low amounts of high molecular weight polymers (e.g., thickeners of at least certain MW, wherein some class of viscosity building polymers are particularly preferred) to further enhance the viscosity of aqueous/aqueous biphasic liquids after they have been stirred/agitated and are in one phase. The amounts cannot be too high without destroying ability to adequately phase separate.